The present invention relates to a lock structure for a seat back of a vehicle seat, having: a striker including multiple engaged portions and provided on a vehicle body side; and an engaging portion provided in a seat back capable of tilting in a vehicle front-rear direction, the engaging portion being configured to selectively engage with any one of the multiple engaged portions to lock the seat back in an inclined posture, an inclination angle of the seat back in the inclined posture being different depending on the selected engaged portion.
Conventionally, the striker includes: a base portion fixed to a lateral portion of the vehicle body; and a striker main body protruding from the base portion toward a vehicle width direction inner side.
The striker main body is formed of an annular rod. The annular rod is supported on the lateral portion of the vehicle body to be turnable about a shaft extending in a vehicle front-rear direction. Moreover, the rod is provided with paired rod portions orthogonal to each other and a first engaged portion and a second engaged portion are formed respectively and individually in the paired rod portions. Furthermore, the rod is turned about the shaft to be switched between a first locking state in which the engaging portion of the seat back engages with the first engaged portion and a second locking state in which the engaging portion engages with the second engaged portion.